We present an preliminary analysis of an on-going Wisconsin H-alpha Mapper (WHAM) survey of the fourth quadrant of the Galactic plane in diffuse emission from [S II] 6716 A, covering fourth galactic quadrant (Galactic longitude=270-360 degrees) and galactic latitude |b|<12 degrees. Because of the high atomic mass and narrow thermal line widths of sulfur (as compared to hydrogen or nitrogen), this emission line serves as the best tracer of the kinematics of the warm ionized medium in the mid plane of the Galaxy. We detect extensive emission at velocities as negative as -100 km/s indicating that we are seeing much further into the center of the Milky Way than was found for the first quadrant. We discuss constraints on the velocity and vertical density structure of this gas, and compare this distribution with what is observed in CO and HI surveys. This work was partially supported by the National Science Foundation's REU program through NSF Award AST-1004881. WHAM research and on-going operations are supported by NSF award AST-1108911.